Highly sensitive non-coding RNA imaging

The motivation – Despite the fact that RNA molecules play key roles in cellular biology, the ability to visualize these important RNAs has been impeded by a lack of biochemical tools like the fluorescent proteins that are available for studying cellular proteins. An ideal system for labelling RNA molecules must be one that does not interfere with biological function; it must respond to light in a way that is similar to that of existing fluorescent proteins; and it must be compatible with established experimental procedures used in the labelling of cell proteins. Developing fluorescent RNA tags is therefore a high priority for biomedical researchers who are driven to uncover the secrets of how RNA plays key roles in cellular processes.

The discovery – The Unrau group at Simon Fraser University and their colleagues from Imperial College London and Université de Strasbourg have developed a set of very bright and high affinity RNA tags called RNA Mango; the base structures of these fluorescent tags are “aptamers,” which are short, single-stranded RNA molecules that bind specifically and selectively to their fluorescent-generating ligand targets. These RNA Mango tags are brighter than the highly useful protein labelling tag known as “enhanced green fluorescent protein,” and they can be inserted into small biological RNAs without altering the cellular localization of those biomolecules. Remarkably, several of these aptamers are highly resistant to formaldehyde – a commonly used fixative for preparing cell samples for microscopy – which allows RNA Mango to be used to image RNA in both live and fixed antibody stained cells.

Its significance – This RNA aptamer–fluorophore system expands the repertoire of tools available to researchers who study biological systems. In particular, this new tool enables the study of RNA function and dynamics in both living and fixed mammalian cells.